In general, the design of a prior-art power circuit uses a plug-and-socket relation for an electric connection to supply power supply to a household electric appliance. Such application is generally used in many countries of the world. The only difference resides on the shape and width of the plugs and sockets.
A plug usually comes with two conductive plates or terminals extended outward for being inserted into a socket hole of a socket. Undeniably, the tight attachment of the two determines the quality of circuit connection; if the attachment is too loose, the conductive plates will be separated from the socket hole easily. Therefore, attention should be paid to the tight attachment for a secured connection.
Based on the safety consideration, it is necessary to have a ground wire or a ground bracket with the grounding effect on the live and neutral plugs or socket as required in many countries such as England and the United States to prevent electric leakage.
Since the safety specifications for plugs and sockets in different countries are different, therefore connectors are divided into 2-terminal connectors and 3-terminal connectors. However, the plug and socket manufacturers usually build a ground terminal on the connector to avoid a high inventory of different extension cords. However, such ground terminals cannot be plugged into the sockets in some countries such as Taiwan and Japan, because there is no ground socket hole for the insertion. Therefore, the design for adapting both 2-terminal and 3-terminal connections comes into place, but the length of the connector after inserting the adaptor will be increased greatly. The increased weight of the connector also causes the connector to fall off from the socket easily. Another solution is to cut off the ground terminal for disabling the grounding function.
Further, in order to avoid the exposure of the live and neutral terminals from the power cables and extension cords for some traveling electric appliances such as an electric razor or an information product, the terminals are designed in an U-shape or contractible form, so that the terminals can be extended outside or withdrawn inside. However, some countries like the United States have strict safety specification on sockets with grounding wire holes. In other words, if the ground terminal is not extended outside, the live and neutral terminals cannot be plugged. Therefore, designing a link assembly to meet the requirements of such specification is a subject for connector manufacturers.